Column by Paul Bonneau.
Exclusive to STR
I vaguely remember when I first discovered logical fallacies (hint: it was not in a government school); I recall being thrilled that there were some boundaries for argumentation that could be used to reject some poor arguments and help find the truth of things. I have long used Stephen Downes’ site  as a particularly good exposition of them, since it also includes instructions how to prove or disprove that a logical fallacy is in fact being used.
But something about them makes me a bit suspicious. For one thing, the ruling class often co-opts worthy concepts for its own ends: education, protection services, and news become indoctrination, police state thuggery and propaganda. Would they uncharacteristically leave logical fallacies alone, untouched and unsullied?
When I first encountered Downes’ site, I avidly read through it. I noticed something funny after a while, when looking at the examples of each fallacy that he provided, of which there were usually two or three per fallacy. There seemed to be a disparity. I started counting the examples of fallacies that might have been mouthed by a conservative, versus the number that might have been mouthed by a liberal. Interestingly, the conservative examples outnumbered the liberal by a large amount. At first I thought, “Well, Downes is a liberal college professor; one would naturally expect this bias.” Although it did make me wonder what his true intention was in publishing that website! I contacted him with this information, certain he’d want to fix his site and remove the bias by evening things out, since an impartial treatment would be more likely to help spread the knowledge of logical fallacies than a biased one would. He responded politely, but essentially blew me off!
Well, one questionable actor does not destroy the legitimacy of a concept; but I noticed something else. It seems every person working in this area has his own list of fallacies, and the lists do not match up. That was a bit worrisome.
And then I started wondering about particular fallacies. Let’s look at Slippery Slope .
First look at example 1, “If we pass laws against fully-automatic weapons, then it won’t be long before we pass laws on all weapons....” Now, it is not too hard to see what is fallacious about willy-nilly stringing together a bunch of “if-thens.” But to disprove it, we need only show that, “this final event need not occur as a consequence of P,” as the proof puts it? That’s it? Nothing more?
If that is all the proof need do, then any predicted sequence of events can always be called a slippery slope, a fallacy, because in the infinite universe of possibilities, in each step there need only be one that does not lead to the final conclusion.
To amplify this point, let’s just take a subset of example 1: “If the government passes laws on all weapons, then they will begin to restrict other rights.” Now, this is not hard to understand, since weapons deter bad actions; and absent the deterrent, more bad actions are likely to occur. But note, that is not 100% certain. What if Ron Paul was elected President just after the previous Congress had banned all weapons? Then we can be pretty sure the government would not start restricting other rights. It doesn’t matter how likely the outcome that is predicted, nor does the record of history matter. According to Downes, we need find only one counter-example and the prediction we are examining becomes a fallacy.
Now one could respond that the sequence could be properly argued by adding the word “probably” in each step. I suppose this is true (if formulaic), but doesn’t it also mean each step must be proved as “probably” true? We cannot trust human intuition on this. How much will the observer (with the typical short attention span) tolerate this? Does the ruling class bother with these niceties? It’s pretty fine for them if they can tie us down with rules that they themselves never bother to obey. In fact, that might be a good definition of “ruling class.”
Another one is Argumentum Ad Hominem .
The third example for that fallacy is, “We should disregard Share B.C.'s argument because they are being funded by the logging industry. (ad hominem circumstantial)”
The proof is, “Identify the attack and show that the character or circumstances of the person has nothing to do with the truth or falsity of the proposition being defended.” In what sense does being funded by an interest group have nothing to do with support for that interest group? Downes is imagining a world filled with dispassionate and non-self interested people. The average man wants to bring home a paycheck to put food on the table for his family. He is going to bite the hand that feeds him and his family, to avoid committing a logical fallacy? I don’t think so!
One of the most important facts in the human world is that people act in their own interest. This overpowers almost everything else. Remember that old “banality of evil” thing?
It’s essentially impossible to prove that any proponent is affected by his character or circumstances, while only the terminally naive would say this means there is no effect!
What good is this fallacy anyway? People have an intuition about these things; they look at who employs the proponent, and this does not seem unwise. That is why proponents look so hard to find a disinterested or even supposedly hostile witness for their point of view. For example, the gun banners have recently taken to enlisting doddering old hunters  in their silly campaign to deny us battle rifles (a smart tactic, but I suspect it won’t work).
I still think the concept of logical fallacies is important, and still think children ought to be taught it (this requires getting your kid out of the government school). But even knowing about the fallacies might not be enough. A certain amount of skepticism based on knowledge of human foibles ought to be part of every education. Eighty percent of the human world is self-serving bullshit. Even the concept of logical fallacies itself, I would argue, can be used that way. So look out for it!